The Collaborative International Dictionary of English v.0.48:

Fraudulent \Fraud"u*lent\, a. [L. fraudulentus, fr. fraus,
   fraudis, fraud: cf. F. fraudulent.]
   1. Using fraud; tricky; deceitful; dishonest.
      [1913 Webster]

   2. Characterized by, founded on, or proceeding from, fraud;
      as, a fraudulent bargain.
      [1913 Webster]

            He, with serpent tongue, . . .
            His fraudulent temptation thus began. --Milton.
      [1913 Webster]

   3. Obtained or performed by artifice; as, fraudulent
      conquest. --Milton.

   Syn: Deceitful; fraudful; guileful; crafty; wily; cunning;
        subtle; deceiving; cheating; deceptive; insidious;
        treacherous; dishonest; designing; unfair.
        [1913 Webster]

WordNet (r) 3.0 (2006):

fraudulent
    adj 1: intended to deceive; "deceitful advertising"; "fallacious
           testimony"; "smooth, shining, and deceitful as thin ice"
           - S.T.Coleridge; "a fraudulent scheme to escape paying
           taxes" [syn: deceitful, fallacious, fraudulent]

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "fraudulent":
   amoral, artful, bent, brigandish, burglarious, calculating,
   chiseling, collusive, conscienceless, corrupt, corrupted,
   counterfeit, covinous, crafty, criminal, crooked, cunning, dark,
   deceitful, deceptive, devious, dishonest, dishonorable,
   double-dealing, doubtful, dubious, duplicitous, evasive, fake,
   false, falsehearted, falsified, felonious, finagling, fishy,
   forged, furtive, guileful, ill-got, ill-gotten, imitation, immoral,
   indirect, insidious, kleptomaniac, larcenous, light-fingered,
   not kosher, pinchbeck, piratelike, piratic, questionable, rotten,
   scheming, shady, sham, shameless, sharp, shifty, sinister,
   slippery, sneaky, spurious, sticky-fingered, surreptitious,
   suspicious, thieving, thievish, treacherous, trickish, tricky,
   two-faced, unconscienced, unconscientious, unconscionable,
   underhand, underhanded, unethical, unprincipled, unsavory,
   unscrupulous, unstraightforward, wily, without remorse,
   without shame